Field of the Invention
The invention relates to a shielding element for electromagnetically shielding an aperture opening, in particular, an opening in a metallic structure, a plug holder or a component housing. The invention also relates to a shielding element for electromagnetically shielding an optoelectronic transceiver.
One known type of optoelectronic transceiver is designed for being plugged in and inserted into a housing configured on a printed circuit board. These plug-in transceivers are intended to be used with data rates of up to 10 Gbit/s. Recent modules are intended to be operated at even higher data rates. One disadvantage is that microwave effects are increased at these high data rates and frequencies. By way of example, housings for receiving plug-in, small form factor pluggable (SFP) transceivers of a small type behave like waveguides above about 11 GHz, and this leads to powerful emissions of electromagnetic radiation. In general, the frequency above which a waveguide behavior occurs depends on the size and geometry of the housings that are used.
Configurations are frequently provided in which a plug holder or a component housing, for example, a housing for holding an optoelectronic transceiver, is located within a metallic structure. The metallic structure is formed by the metallic rear wall of a computer housing. In order to insert a plug-in transceiver, or a more general form of a plug-in structure, into the associated plug holder or into a component housing, an aperture opening is formed in the metallic structure. This aperture opening corresponds to the plug holder or to the component housing. In particular, when the plug-in structure is not plugged in, that is to say when the aperture opening is open and is not closed by the plug-in structure, there is a risk of undesirable emission of electromagnetic radiation from the interior of the metallic structure to the exterior.
It is accordingly an object of the invention to provide a shielding element for electromagnetically shielding an aperture opening, which provides effective and reliable shielding of the aperture opening with respect to radio-frequency electromagnetic radiation, especially in the situation when no plug-in element is inserted into the aperture opening.
With the foregoing and other objects in view there is provided, in accordance with the invention, a shielding element for electromagnetically shielding an aperture opening and for receiving a plug-in element. The shielding element includes: a frame defining an aperture opening, and a plurality of conductive contact springs extending from the frame towards the aperture opening. In a non-deflected state, the plurality of the contact springs at least partially overlap one another and close the aperture opening. As a plug-in element is being inserted in an insertion direction into the aperture opening, the plurality of the contact springs are deflected in the insertion direction and rest in a sprung manner on the plug-in element.
In other words, a large number of conductive contact springs are formed on a frame of the shielding element, which extend into the interior of the aperture opening. In the non-deflected state, the individual contact springs at least partially overlap one another, so that the aperture opening is closed. When a plug-in element is inserted into the aperture opening, the contact springs are deflected in the insertion direction and rest in a sprung manner on the plug-in element. In the process, the contact springs preferably make electrical contact with electrically conductive structures of the plug-in element, in particular with a metallic housing or a shielding structure, so that any potential differences that occur can be dissipated.
The invention is based on the idea that when no plug-in element or plug-in structure is inserted in the aperture opening, the individual contact springs close the aperture opening, and in the process form a conductive barrier or shield for electromagnetic waves. When a component is inserted, the contact springs (which are bent inward by the plug-in element) form an effective contact for the corresponding shielding structure of the element. An automatically closing radio-frequency seal is thus provided for electromagnetic radiation, which automatically closes an aperture opening, for example, in a metallic structure, a plug holder, or component housing, when no component, for example, a plug, etc. is inserted. That is to say when the plug-in location is not in use. At the same time, a sprung, conductive contact is made with the plug-in component.
For the purposes of the present invention, the term frame should be understood as meaning any structure that is suitable for supporting and for holding contact springs that extend into an aperture opening. The frame need not in this case be completely circumferential, and in the extreme case, can be formed by just a straight web.
In one preferred refinement of the invention, groups of contact springs are provided, which each extend from one face of the frame into the interior of the aperture opening. An intermediate space is provided between the individual groups on the opened and unbent shielding element in order to ensure that the interlaced springs can be restored to their original position after the plug-in component has been withdrawn, and to prevent the springs from becoming caught. The contact springs are essentially rectangular and preferably have angled ends. The ends of opposite contact springs are preferably angled in opposite directions. This ensures that the contact springs are reliably interlaced. It is also possible for the contact springs to have different lengths, so that they can be interlaced better.
In one preferred embodiment, the frame is a hollow body formed as a cuboid casing. However, other forms may also be provided. For example, the hollow body may be in the form of a cylindrical casing. It should also be mentioned that the frame need not necessarily be designed such that it is closed. A closure for an aperture opening can also be provided, for example, by contact springs that are configured on three sides of a rectangular frame that is open on one side. The contact springs extend towards the aperture opening. In the extreme case, a closure for an aperture opening may even be provided by contact springs that are formed on only one side of a frame.
In the non-deflected state, the contact springs are preferably bent through an angle of 90xc2x0 from the one end face of the hollow body. Further contact springs may be formed on the other side of the hollow body. These are bent back through an angle of approximately 180xc2x0 onto the outer surface of the hollow body and are used to make contact between the shielding element and a metallic structure, in particular a metallic rear wall of a computer housing in which the aperture opening is located. The shielding element in this case is inserted into the aperture opening.
Latching hooks are furthermore preferably provided on the hollow body. These are used, for example, for connecting the shielding element to a plug holder or to a component housing. In this case, the shielding element is a separate component, which is plugged onto a plug holder or a component housing, or is connected to such elements in some other way. However, it is likewise possible for the shielding element to be part of a plug holder or of a component housing, thus representing an integrated unit with the plug holder or component housing.
In a further refinement of the invention, the frame lies essentially in the same plane as the non-deflected contact springs, and in this case, has no extent or only a short extent at right angles to this plane. In particular, the frame is a rectangular frame. A device for mounting on a further structure, in particular on a metallic rear wall, is preferably provided on the frame. This device can be, for example, contact and mounting tabs that project outward and that can be conductively adhesively bonded, soldered or welded to a metallic rear wall.
The plane in which the contact springs are located and the plane in which the contact and mounting tabs are located are in this case preferably offset with respect to one another. The contact springs are thus preferably angled away from one end face, and the contact and mounting tabs are preferably angled away from the other end face of the frame. The frame in this case forms an edge, which can be inserted in an interlocking manner into the opening in a rear wall.
The shielding element is preferably formed in one operation by bending segments of a rectangular, open material strip, with the contact springs being formed on one longitudinal face of the material strip. This ensures that they can be manufactured easily from simple geometric shapes.
The contact springs are preferably formed integrally with the shielding element. The shielding element is composed of a highly conductive material, for example a stamped sheet-metal part which is bent in some suitable manner.
It is within the scope of the invention for an additional frame to be provided for holding and/or mounting the shielding element and/or for fixing a plug-in component which is inserted into the aperture opening. A material which absorbs electromagnetic rays or an additionally shielding material, for example an EMI (electromagnetic interference) wire mesh or an EMI foam seal, may also be used.
In accordance with an added feature of the invention, the contact springs are configured into groups and each one of the groups of the contact springs includes three or four contact springs.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a shielding element for electromagnetic shielding of an aperture opening, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.